Services for providing digital content may generally be classified into two categories: subscription-based or non-subscription-based. With subscription-based services, the user must first subscribe to the service, which often entails payment of a subscription fee or payment on a per use basis. The content provided by subscription-based services may vary and may include contents such as journal articles, databases, financial information and the like.
Non-subscription-based services do not require that a user have a subscription in order to access information provided by the service. Search engines, such as those provided by Yahoo and Netscape, are examples of non-subscription based services. A user may submit a request to the search engine and receive search results that contain a number of hyperlinks to content available on the Internet without having a subscription.
One current difficulty facing users is that content provided by subscription-based services and content provided by non-subscription based services are distinct and must be queried separately. For example, if a user is interested in information about astronauts, the user must first submit a query to the subscription-based service to obtain search results. Subsequently, the user must submit a separate query to the non-subscription-based service.
Another difficulty concerns hyperlinks within documents. A hyperlink within a document works well so long as the reader of the document has access to the content referenced by the hyperlink. Difficulties may arise where the hyperlink references content that is not accessible to the reader. In many instances, the hyperlink refers purely to content that is freely accessible and, thus, is unduly limiting in its scope.